Hugh Grosvenor, the Duke of Westminster, was worth nearly £10 billion before turning 40 — and he still owns roughly 300 acres of Mayfair and Belgravia that the family has refused to sell for three centuries
Hugh Grosvenor became the 7th Duke of Westminster at 25 with a £9.9 billion fortune built on 300 acres of Mayfair and Belgravia — land his family has leased, but never sold, since 1677.